The invention relates to a servicing apparatus which can be moved along a spinning machine and has devices for seeking and winding a yarn end from a spool package of a spinning unit. These devices contain an auxiliary driving roller which can be applied to the circumference of the spool package and, at a distance from this auxiliary driving roller, a yarn seeking nozzle which can be moved into a seeking position in direct proximity of the circumference of the spool package by means of an adjusting drive. This invention also relates to a method of operating a servicing apparatus to precisely locate the yarn seeking nozzle.
An arrangement of this type is described in U.S. patent application Ser. No. 07/350,350 filed May 11, 1989, now U.S. Pat. No. 5,016,432. Since in this arrangement the yarn seeking nozzle is applied to the spool package at a distance from the auxiliary driving roller, the filling ratio of the spool package considerably influences the precision with which the yarn seeking nozzle is positioned with respect to the spool package. If, on the other hand, the yarn seeking nozzle is arranged in close proximity of the auxiliary driving roller, the filling ratio of the spool package is unimportant. However, in practice, it is not always possible to implement this type of an arrangement.
An object of the invention is to construct a servicing apparatus of the initially mentioned type in such a manner that, irrespective of the diameter of the spool package, a precise adjustment of the yarn seeking nozzle is achieved in its seeking position, at any time.
This object is achieved in that devices are provided for the adapting of the seeking position of the yarn seeking nozzle to the respective diameter of the spool package.
By means of this construction, it is achieved that the yarn seeking nozzle is always applied to the circumference of the spool package at a precise constant distance so that the functioning of the yarn seeking nozzle is constantly ensured.
In a further development of preferred embodiments of the invention, it is provided that the adjusting drive is provided with a control device to which devices are assigned for the sensing of the diameter of the spool package. A sort of measuring of the diameter of the spool package takes place in this case which may be either directly or indirectly.
In another construction of the invention, it is provided that the yarn seeking nozzle is equipped with a switch which switches its adjusting drive and determines the reaching of the circumference of the spool package. This may, for example, be a mechanical limit switch. However, it may also be provided that the adjusting drive of the yarn seeking nozzle is equipped with a switching element which determines its striking against the spool package which acts as a stop, in which case the control of the adjusting drive will then expediently cause the yarn seeking nozzle to lift itself off again by a certain distance from the circumference of the spool package.
In another embodiment of the invention, it is provided that the devices for the sensing of the diameter of the spool package are constructed as devices which sense the applied position of the auxiliary driving roller. This auxiliary driving roller is applied to the circumference of the spool package anyhow, adapting its position to the diameter of the spool package. The position which will then be taken up by the auxiliary driving roller may also be analyzed as a signal indicating the diameter of the spool package.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.